Fig. 4. Cell proliferation in the developing chick retina, as detected by BrdU incorporation. Staining with a monoclonal antibody to BrdU results in a brown reaction product. No increase in cell proliferation was detected in the optic nerve region (A,B) of the central retina, in regions neighboring the optic nerve region (C,D; higher magnification of region resembling area of insets in Fig. 3A,B) or in more peripheral regions (E,F; higher magnification of the proliferation zone) when comparing control (A,C,E) and anti-TGF-ß-treated (B,D,F) retinae. (G) Quantification of cell proliferation. Comparison shown as number of BrdU-positive cells in control versus anti-TGF-ß-treated retinae. nr, neural retina; on, optic nerve; ov optic ventricle; pe, pigment epithelium. Scale bars: in A, 100 µm for A,B; in C, 50 µm for C,D; in E, 50 µm for E,F.